In household electrical appliances, AV devices, PC/OA devices, industrial machinery, and other electrical devices, touch switch panels involving projected capacitance schemes are used as one type of input means. In a projected capacitance scheme, a plurality of sensor electrodes are arrayed in a grid configuration along an X direction and a Y direction. Projected capacitive touch switch panels are typically configured from X-direction and Y-direction transparent sensor electrode layers formed of indium tin oxide (“ITO”), a wiring layer leading to the electrodes, an insulation layer (dielectric layer) provided between transparent electrodes, a surface-protective layer, and the like, the projected capacitive touch switch panels having external control units. When the panel surface is touched by a finger, capacitive coupling occurs between the sensor electrodes and the finger, changing the capacitance of the sensor electrodes. The control unit quantifies the amount of change in the capacitance of the sensor electrodes, and assesses that a finger has touched [the panel surface] when the quantity exceeds a predetermined threshold value. This makes it possible for the control unit to detect which position (XY coordinates on a plane) has been touched by the finger.
One structure known as a specific structure of a projected capacitive touch switch panel is configured such that X-direction transparent sensor electrodes are formed on one glass substrate, a Y-direction transparent sensor electrode layer is formed on another glass substrate, and the glass substrates are superposed so that one of the glass substrates is positioned between the transparent sensor electrodes, constituting an insulation layer (dielectric layer). In another proposed structure, transparent sensor electrodes are formed of ITO on each of two glass substrates, the transparent sensor electrodes are arranged so as to face each other, the glass substrates are superposed with a spacer member interposed therebetween, and a dielectric material is injected between the transparent sensor electrodes (see Patent Document 1). Similarly, a structure was proposed in which transparent sensor electrodes are formed of ITO on each of two glass substrates, the transparent sensor electrodes are arranged so as to face each other, and an insulating adhesive layer is formed between the transparent sensor electrodes (see Patent Document 2).